Reagent-free mechanical patterning of gelatin surfaces by two-step electron irradiation treatment

Spatial control of mechanical properties of hydrogels such as gelatin is of high interest in order to develop highly functionalized substrates for applications in tissue engineering and biomedicine. Established methods to mechanically pattern hydrogels, including photolithography and ink-jet printing, employ additional reagents to induce changes in the network towards local differences in stiffness. Due to possible toxicity of these incorporated agents, reagent-free techniques are highly desirable for any biomedical field of application. Within the present work, we introduce a two-step process in which the focused electron beam of an electron beamlithography system is first utilized to obtain mechanical patterns in mu m-range on air-dried gelatin substrates without any additional reagents. In a second step, these functionalized gelatin substrates are stabilized against gel-sol-transition for physiological conditions by global electron irradiation in the hydrated state by induction of polymer crosslinking. This work investigates precise mechanical patterning of gelatin obtained by this two-step functionalization process using first local and then global electron irradiation. Therefore, structural and mechanical characterization was performed by atomic force microscopy in the air-dried and rehydrated state. These qualitative and quantitative analyses show that excellent mechanical patterning of gelatin hydrogels can be achieved by the presented reagent-free two-step process. (C) 2018 Elsevier Ltd. All rights reserved.